Effect of the protein kinase C inhibitor GF 109 203X on elastase release and respiratory burst of human neutrophils.

1. The effects of bisindolylmaleimide GF 109 203X, reported to be a potent and highly selective inhibitor of protein kinase C (PKC), have been investigated on some human neutrophil functions. 2. GF 109 203X prevented O.2- production by NADPH-oxidase whatever the stimulus used for polymorphonuclear neutrophil (PMN) activation: directs PKC activators like phorbol myristate acetate (PMA) and dioctanoylglycerol, calcium ionophore (A23187), or receptor agonists like fMet-Leu-Phe (fMLP) and opsonized zymosan. 3. The effect of GF 109 203X was also examined on elastase exocytosis by neutrophils. PMA-mediated release was prevented by GF 109 203X. However, GF 109 203X had no effect on exocytosis induced by A23187 and the effect of this compound on the fMLP response changed according to its concentration. 4. These data suggest that PKC might be essential for stimulus-mediated O.2- production and also that PKC plays only a minor role in elastase secretion as compared to the role of the cytosolic calcium level.

A rapid density gradient technique for separating polymorphonuclear granulocytes.

A gradient separation technique followed by isotonic ammonium chloride haemolysis was compared with two methods for the isolation of polymorphonuclear neutrophils from blood. This technique provided a high yield, excellent purity without lymphocyte and erythrocyte contamination, and made it possible to isolate more than 50 x 10(6) human neutrophils from 15 ml of blood. The polymorphonuclear neutrophils isolated in this way were capable of generating a large amount of reactive oxygen species. This technique for the separation of polymorphonuclear neutrophils is an effective method for in vitro studies.

Decrease of hypochlorous acid and hydroxyl radical generated by stimulated human neutrophils: comparison in vitro of some thiol-containing drugs.

Among reactive oxygen species generated by human neutrophils during inflammatory disorders, hypochlorous acid and hydroxyl radical are especially involved in many diseases such as arteriosclerosis or emphysema. It was shown in vitro that two thiol-containing drugs, mesna and N-acetylcysteine, have antioxidant properties towards these oxidants. The 50% inhibitory concentrations (IC50s) of mesna and N-acetylcysteine for hypochlorous acid production by stimulated neutrophils were 29 and 30 mcM, respectively, and for hydroxyl radical production, IC50s were 520 and 480 mcM, respectively. With this in vitro demonstrated effectiveness, both mesna and N-acetylcysteine have been considered as therapeutic antioxidants to decrease tissue damage inflicted by an excess of activated neutrophils by scavenging hypochlorous acid and hydroxyl radical.

Comparison of in vitro effects of two thiol-containing drugs on human neutrophils hydrogen peroxide production.

During inflammatory disorders, potentially destructive reactive oxygen species, especially hydrogen peroxide, are produced by activated phagocytic cells. It was demonstrated in vitro that mesna and N-acetylcysteine (NAC), mucolytic thiols, have antioxidant properties. An estimation was made of the 50% inhibitory concentration (IC50) of mesna and NAC for PMA-induced H2O2 production by human neutrophils, the results being 70 mcM and 77 mcM, respectively. The mechanism which governs mesna and NAC reactions results from a scavenging effect of H2O2: the calculated IC50s of this effect were 30 mcM and 42 mcM, respectively, in free cellular experimentation. The results suggest that mesna and NAC might be used as antioxidants in aerosols to prevent tissue damage inflicted by this reactive oxygen species, especially in the lungs.

Effectiveness of earplugs in high-intensity impulse noise.

The efficiency of different types of earplugs was assessed by means of Békésy audiometry following the exposure of 42 human subjects to weapon impulses. The peak pressure of the impulses ranged from 2.3-27.8 kPa (from 161 to 183-dB peak SPL) and the A-weighted equivalent level (over 8 h) of each exposure ranged from 100-114 dB. All subjects wore earplugs fitted by an experienced individual. The devices tested included one brand of conventional foam earplugs and a number of different models of perforated earplugs, one type of which had been previously shown to provide nonlinear attenuation. Perforated earplugs were tested because they provide better speech communication than conventional passive earplugs, and in the nonlinear case also afford attenuation that increases with the peak pressure of the impulses. The temporary threshold shifts (TTSs) observed in these experiments were very small and indicated no significant hazard for hearing. Well-fitted perforated earplugs seem to be able to protect the ear from infrequent exposures to the high-level impulses produced by small and large weapons while allowing good speech communication, and without impairing the operational capacity of soldiers who must remain aware of their acoustic environment.

Delayed temporary threshold shift induced by impulse noises (weapon noises) in men.

Most of the available information on the effects of impulse noise on hearing is derived from temporary threshold shift (TTS2) measurements performed 2 min after a single exposure to small-weapon noises. TTS is known to recover as a linear function of the logarithm of time when it is induced by a continuous noise of moderate intensity. Following the exposure to impulse noise, several investigators have reported individual exceptions to the log-time relation, e.g. increases in TTS during the first hour of recovery. These authors observed a 'rebound recovery function' for most of the exposed men, and they conclude that this phenomenon '... has implications for the use of TTS in the construction of damage risk criteria for hazardous noise exposure ..., a single measure, such as the widely used TTS2 may not be an adequate index of the magnitude of the TTS'. In order to thoroughly investigate in man the existence of 'delayed' TTS following the exposure to actual weapon noises, the 'French Committee on Weapon Noises' carried out the following study. Three groups of soldiers (28 subjects) wearing no hearing protection were exposed in the free field over 2 days to impulse noises produced by a rifle. Békésy audiograms were obtained from each subject just before the exposure, and at 5 min, 1 h and 4 h after exposure. All audiometric tests were carried out even when no TTS was observable in the first postexposure audiogram. A significant number of subjects showed a 'delayed TTS' and/or 'rebound recovery'. The maximum TTS was observed at 1 h after exposure, but the observation of a delayed recovery and a rebound recovery indicate that audiometric tests should be performed in all cases at least up to 4 h after the exposure. More detailed work is necessary to establish what changes may be necessary in the present damage risk criteria for impulse noises of a very high level.